RESUMO
Plasmodium falciparum infection and malaria remain a risk for millions of children and pregnant women. Here, we seek to integrate knowledge of mouse and human T helper cell (Th) responses to blood-stage Plasmodium infection to understand their contribution to protection and pathology. Although there is no complete Th subset differentiation, the adaptive response occurs in two phases in non-lethal rodent Plasmodium infection, coordinated by Th cells. In short, cellular immune responses limit the peak of parasitemia during the first phase; in the second phase, humoral immunity from T cell-dependent germinal centers is critical for complete clearance of rapidly changing parasite. A strong IFN-γ response kills parasite, but an excess of TNF compared with regulatory cytokines (IL-10, TGF-ß) can cause immunopathology. This common pathway for pathology is associated with anemia, cerebral malaria, and placental malaria. These two phases can be used to both understand how the host responds to rapidly growing parasite and how it attempts to control immunopathology and variation. This dual nature of T cell immunity to Plasmodium is discussed, with particular reference to the protective nature of the continuous generation of effector T cells, and the unique contribution of effector memory T cells.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Malária Falciparum/imunologia , Placenta/patologia , Plasmodium falciparum/patogenicidade , Animais , Linfócitos T CD4-Positivos/metabolismo , Citocinas/metabolismo , Feminino , Humanos , Imunidade Celular , Imunidade Humoral , Ativação Linfocitária , Malária Falciparum/parasitologia , Malária Falciparum/patologia , Camundongos , Fenótipo , Placenta/imunologia , Placenta/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium falciparum/imunologia , Gravidez , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Auxiliares-Indutores/metabolismoRESUMO
CD4 T cells are required, along with antibodies, for complete protection from blood-stage infection with Plasmodium spp., which cause malaria. Without continuous exposure, as on emigration of people from endemic areas, protection from malaria decays. As in other persistent infections, low-level Plasmodium chabaudi infection protects the host from reinfection at 2 months postinfection, a phenomenon termed premunition. Premunition is correlated with T cell responses, rather than antibody levels. We previously showed that while both effector T cells (Teff) and memory T cells (Tmem) are present after infection, Teff protect better than Tmem. Here, we studied T cell kinetics post-infection by labeling dividing Ifng+ T cells with 5-bromo-2'-deoxyuridine (BrdU) in infected Ifng reporter mice. Large drops in specific T cell numbers and Ifng+ cells upon clearance of parasites suggest a mechanism for decay of protection. Although protection decays, CD4 Tmem persist, including a highly differentiated CD27- effector memory (Tem) subset that maintains some Ifng expression. In addition, pretreatment of chronically infected animals with neutralizing antibody to interferon gamma (IFN-γ) or with clodronate liposomes before reinfection decreases premunition, supporting a role for Th1-type immunity to reinfection. A pulse-chase experiment comparing chronically infected to treated animals showed that recently divided Ifng+ T cells, particularly IFN-γ+ TNF+ IL-2- T cells, are promoted by persistent infection. These data suggest that low-level persistent infection reduces CD4+ Tmem and multifunctional Teff survival, but promotes IFN-γ+ TNF+ IL-2- T cells and Ifng+ terminally differentiated effector T cells, and prolongs immunity.
Assuntos
Citocinas , Malária , Animais , Camundongos , Linfócitos T CD4-Positivos , Citocinas/metabolismo , Interferon gama/metabolismo , Interleucina-2 , Infecção Persistente , Reinfecção/metabolismo , Subpopulações de Linfócitos T , Células Th1/imunologiaRESUMO
BACKGROUND: Excess tumor necrosis factor (TNF) is implicated in the pathogenesis of hyperinflammatory experimental cerebral malaria (eCM), including gliosis, increased levels of fibrin(ogen) in the brain, behavioral changes, and mortality. However, the role of TNF in eCM within the brain parenchyma, particularly directly on neurons, remains underdefined. Here, we investigate electrophysiological consequences of eCM on neuronal excitability and cell signaling mechanisms that contribute to observed phenotypes. METHODS: The split-luciferase complementation assay (LCA) was used to investigate cell signaling mechanisms downstream of tumor necrosis factor receptor 1 (TNFR1) that could contribute to changes in neuronal excitability in eCM. Whole-cell patch-clamp electrophysiology was performed in brain slices from eCM mice to elucidate consequences of infection on CA1 pyramidal neuron excitability and cell signaling mechanisms that contribute to observed phenotypes. Involvement of identified signaling molecules in mediating behavioral changes and sickness behavior observed in eCM were investigated in vivo using genetic silencing. RESULTS: Exploring signaling mechanisms that underlie TNF-induced effects on neuronal excitability, we found that the complex assembly of fibroblast growth factor 14 (FGF14) and the voltage-gated Na+ (Nav) channel 1.6 (Nav1.6) is increased upon tumor necrosis factor receptor 1 (TNFR1) stimulation via Janus Kinase 2 (JAK2). On account of the dependency of hyperinflammatory experimental cerebral malaria (eCM) on TNF, we performed patch-clamp studies in slices from eCM mice and showed that Plasmodium chabaudi infection augments Nav1.6 channel conductance of CA1 pyramidal neurons through the TNFR1-JAK2-FGF14-Nav1.6 signaling network, which leads to hyperexcitability. Hyperexcitability of CA1 pyramidal neurons caused by infection was mitigated via an anti-TNF antibody and genetic silencing of FGF14 in CA1. Furthermore, knockdown of FGF14 in CA1 reduced sickness behavior caused by infection. CONCLUSIONS: FGF14 may represent a therapeutic target for mitigating consequences of TNF-mediated neuroinflammation.
Assuntos
Comportamento de Doença , Malária Cerebral , Camundongos , Animais , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Inibidores do Fator de Necrose Tumoral , Canal de Sódio Disparado por Voltagem NAV1.6/metabolismo , Neurônios/metabolismo , Transdução de SinaisRESUMO
Protection at the peak of Plasmodium chabaudi blood-stage malaria infection is provided by CD4 T cells. We have shown that an increase in Th1 cells also correlates with protection during the persistent phase of malaria; however, it is unclear how these T cells are maintained. Persistent malaria infection promotes protection and generates both effector T cells (Teff), and effector memory T cells (Tem). We have previously defined new CD4 Teff (IL-7Rα-) subsets from Early (TeffEarly, CD62LhiCD27+) to Late (TeffLate, CD62LloCD27-) activation states. Here, we tested these effector and memory T cell subsets for their ability to survive and protect in vivo. We found that both polyclonal and P. chabaudi Merozoite Surface Protein-1 (MSP-1)-specific B5 TCR transgenic Tem survive better than Teff. Surprisingly, as Tem are associated with antigen persistence, Tem survive well even after clearance of infection. As previously shown during T cell contraction, TeffEarly, which can generate Tem, also survive better than other Teff subsets in uninfected recipients. Two other Tem survival mechanisms identified here are that low-level chronic infection promotes Tem both by driving their proliferation, and by programming production of Tem from Tcm. Protective CD4 T cell phenotypes have not been precisely determined in malaria, or other persistent infections. Therefore, we tested purified memory (Tmem) and Teff subsets in protection from peak pathology and parasitemia in immunocompromised recipient mice. Strikingly, among Tmem (IL-7Rαhi) subsets, only TemLate (CD62LloCD27-) reduced peak parasitemia (19%), though the dominant memory subset is TemEarly, which is not protective. In contrast, all Teff subsets reduced peak parasitemia by more than half, and mature Teff can generate Tem, though less. In summary, we have elucidated four mechanisms of Tem maintenance, and identified two long-lived T cell subsets (TemLate, TeffEarly) that may represent correlates of protection or a target for longer-lived vaccine-induced protection against malaria blood-stages.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Memória Imunológica/imunologia , Malária/imunologia , Malária/prevenção & controle , Plasmodium chabaudi/imunologia , Subpopulações de Linfócitos T/imunologia , Animais , Interferon gama/biossíntese , Malária/patologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BLRESUMO
Understanding the mechanisms of CD4 memory T cell (Tmem) differentiation in malaria is critical for vaccine development. However, the metabolic regulation of CD4 Tmem differentiation is not clear, particularly in persistent infections. In this study, we investigated the role of fatty acid synthesis (FAS) in Tmem development in Plasmodium chabaudi chronic mouse malaria infection. We show that T cell-specific deletion and early pharmaceutical inhibition of acetyl CoA carboxylase 1, the rate limiting step of FAS, inhibit generation of early memory precursor effector T cells (MPEC). To compare the role of FAS during early differentiation or survival of Tmem in chronic infection, a specific inhibitor of acetyl CoA carboxylase 1, 5-(tetradecyloxy)-2-furoic acid, was administered at different times postinfection. Strikingly, the number of Tmem was only reduced when FAS was inhibited during T cell priming and not during the Tmem survival phase. FAS inhibition during priming increased effector T cell (Teff) proliferation and strongly decreased peak parasitemia, which is consistent with improved Teff function. Conversely, MPEC were decreased, in a T cell-intrinsic manner, upon early FAS inhibition in chronic, but not acute, infection. Early cure of infection also increased mitochondrial volume in Tmem compared with Teff, supporting previous reports in acute infection. We demonstrate that the MPEC-specific effect was due to the higher fatty acid content and synthesis in MPEC compared with terminally differentiated Teff. In conclusion, FAS in CD4 T cells regulates the early divergence of Tmem from Teff in chronic infection.
Assuntos
Ácidos Graxos/biossíntese , Memória Imunológica , Infecções/imunologia , Infecções/metabolismo , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Acetil-CoA Carboxilase/deficiência , Transferência Adotiva , Animais , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Sobrevivência Celular/genética , Doença Crônica , Regulação da Expressão Gênica , Interações Hospedeiro-Parasita/imunologia , Infecções/genética , Infecções/microbiologia , Metabolismo dos Lipídeos , Ativação Linfocitária/imunologia , Malária/genética , Malária/imunologia , Malária/metabolismo , Malária/parasitologia , Camundongos , Camundongos Transgênicos , Mitocôndrias/genética , Mitocôndrias/imunologia , Receptor fas/genética , Receptor fas/metabolismoRESUMO
Malaria-associated bacteremia accounts for up to one-third of deaths from severe malaria, and non-typhoidal Salmonella (NTS) has been reported as a major complication of severe malarial infection. Patients who develop NTS bacteremia during Plasmodium infection show higher mortality rates than individuals with malaria alone. Systemic bacteremia can be caused by a wound or translocation from epithelial or endothelial sites. NTS is an intestinal pathogen, however the contribution of bacterial translocation from the intestinal tract during Plasmodium infection is not well studied. Here, we investigated the integrity of the intestinal barrier function of P. chabaudi-infected mice using large molecules and Salmonella infection. Intestinal histology and the adaptive immune response to malaria were also studied using light microscopy and flow cytometry. P. chabaudi infection compromised intestinal barrier function, which led to increased intestinal cellular infiltration. In addition, we observed increased serum lipopolysaccharide binding protein and leakage of soluble molecules from the intestine into the blood in infected mice. Plasmodium infection also increased intestinal translocation and dissemination of NTS to the liver. The adaptive immune response to P. chabaudi infection was also significantly impacted by NTS translocation. Reduced B and T cell activation were observed in co-infected animals, suggesting interference in the malaria-specific immune responses by bacteremia. These studies demonstrate that P. chabaudi infection induces failure of the barrier function of the intestinal wall and enhanced intestinal bacterial translocation, affecting anti-malarial immunity.
Assuntos
Imunidade Adaptativa , Malária/imunologia , Plasmodium chabaudi/imunologia , Infecções por Salmonella/imunologia , Salmonella/imunologia , Animais , Bacteriemia , Coinfecção , Modelos Animais de Doenças , Feminino , Microbioma Gastrointestinal , Intestinos/microbiologia , Intestinos/patologia , Ativação Linfocitária , Malária/complicações , Malária/parasitologia , Malária/patologia , Camundongos , Camundongos Endogâmicos C57BL , Parasitemia , Infecções por Salmonella/complicações , Infecções por Salmonella/microbiologia , Infecções por Salmonella/patologiaRESUMO
BACKGROUND: Cerebral malaria (CM) is the most lethal outcome of Plasmodium infection. There are clear correlations between expression of inflammatory cytokines, severe coagulopathies, and mortality in human CM. However, the mechanisms intertwining the coagulation and inflammation pathways, and their roles in CM, are only beginning to be understood. In mice with T cells deficient in the regulatory cytokine IL-10 (IL-10 KO), infection with Plasmodium chabaudi leads to a hyper-inflammatory response and lethal outcome that can be prevented by anti-TNF treatment. However, inflammatory T cells are adherent within the vasculature and not present in the brain parenchyma, suggesting a novel form of cerebral inflammation. We have previously documented behavioral dysfunction and microglial activation in infected IL-10 KO animals suggestive of neurological involvement driven by inflammation. In order to understand the relationship of intravascular inflammation to parenchymal dysfunction, we studied the congestion of vessels with leukocytes and fibrin(ogen) and the relationship of glial cell activation to congested vessels in the brains of P. chabaudi-infected IL-10 KO mice. METHODS: Using immunofluorescence microscopy, we describe severe thrombotic congestion in these animals. We stained for immune cell surface markers (CD45, CD11b, CD4), fibrin(ogen), microglia (Iba-1), and astrocytes (GFAP) in the brain at the peak of behavioral symptoms. Finally, we investigated the roles of inflammatory cytokine tumor necrosis factor (TNF) and coagulation on the pathology observed using neutralizing antibodies and low-molecular weight heparin to inhibit both inflammation and coagulation, respectively. RESULTS: Many blood vessels in the brain were congested with thrombi containing adherent leukocytes, including CD4 T cells and monocytes. Despite containment of the pathogen and leukocytes within the vasculature, activated microglia and astrocytes were prevalent in the parenchyma, particularly clustered near vessels with thrombi. Neutralization of TNF, or the coagulation cascade, significantly reduced both thrombus formation and gliosis in P. chabaudi-infected IL-10 KO mice. CONCLUSIONS: These findings support the contribution of cytokines, coagulation, and leukocytes within the brain vasculature to neuropathology in malaria infection. Strikingly, localization of inflammatory leukocytes within intravascular clots suggests a mechanism for interaction between the two cascades by which cytokines drive local inflammation without considerable cellular infiltration into the brain parenchyma.
Assuntos
Citocinas/metabolismo , Gliose/etiologia , Gliose/prevenção & controle , Malária Cerebral/complicações , Vasculite do Sistema Nervoso Central/etiologia , Amônia/sangue , Animais , Anticorpos/uso terapêutico , Anticoagulantes/uso terapêutico , Vasos Sanguíneos/patologia , Modelos Animais de Doenças , Fibrinogênio/metabolismo , Regulação da Expressão Gênica/genética , Proteína Glial Fibrilar Ácida/metabolismo , Gliose/tratamento farmacológico , Heparina/uso terapêutico , Interleucina-10/genética , Interleucina-10/metabolismo , Leucócitos/patologia , Fígado/metabolismo , Fígado/patologia , Malária Cerebral/mortalidade , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Plasmodium chabaudi/fisiologia , Fator de Necrose Tumoral alfa/imunologia , Fator de Necrose Tumoral alfa/metabolismo , Vasculite do Sistema Nervoso Central/tratamento farmacológico , Vasculite do Sistema Nervoso Central/parasitologiaRESUMO
In 2001, The American Association of Immunologists Committee on the Status of Women conducted a survey examining the percentage of women faculty members within immunology departments or women in immunology graduate programs across 27 institutions in the United States, comparing it to the percentage of women receiving a Ph.D. Here, we examine the representation of women across these same 27 immunology departments and programs to examine changes in gender equity over the last 15 years.
Assuntos
Academias e Institutos/estatística & dados numéricos , Alergia e Imunologia , Educação de Pós-Graduação , Docentes/estatística & dados numéricos , Universidades , Mulheres , Alergia e Imunologia/educação , Feminino , Humanos , Estados Unidos , Recursos HumanosRESUMO
Exposure to blood-stage malaria infection is often persistent, leading to generation of CD4 effector and effector memory T cells that contribute to protection. We showed previously that chronic exposure to blood-stage Plasmodium chabaudi offers the best protection from parasitemia and pathology in reinfection cases, correlating with an increase in Th1 cells. Although much is known about the features of resting or exhausted memory T cells (Tmem), little is known about the functional capacities of chronically stimulated but protective T cells. To determine the functional capacity of CD4 T cells generated by chronic infection upon reexposure to parasite, we compared their responses to known features of classical Tmem. The numbers of cytokine-producing T cells increased following infection in the polyclonal populations, suggesting an increase in pathogen-specific T cells. Malaria antigen-specific B5 T cell receptor (TCR) transgenic (Tg) T cells from chronic infection proliferated on reinfection and were highly sensitive to TCR stimulation without costimulation, as shown for Tmem in acute stimulations. However, B5 Tmem did not accumulate more than naive B5 T cells in vivo or in vitro and became apoptotic. Failure to accumulate was partly the result of chronic stimulation, since eliminating persistent parasites before reinfection slightly increased the accumulation of B5 Tg T cells upon reinfection. The levels of specific gamma interferon-positive, interleukin-10-positive T cells, which protect animals from pathology, increased after malaria infection. These data demonstrate that although chronic infection generates a protective T cell population with increased TCR sensitivity and cytokine production, they do not reexpand upon reexposure due to increased apoptosis.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Memória Imunológica , Malária/imunologia , Malária/parasitologia , Plasmodium chabaudi/imunologia , Animais , Apoptose/imunologia , Contagem de Linfócito CD4 , Linfócitos T CD4-Positivos/metabolismo , Epitopos de Linfócito T/imunologia , Feminino , Interleucina-10/biossíntese , Ativação Linfocitária/imunologia , Malária/metabolismo , Camundongos , Receptores de Antígenos de Linfócitos T/metabolismo , Células Th1/imunologia , Células Th1/metabolismoRESUMO
CD4 T cells orchestrate immunity against blood-stage malaria. However, a major challenge in designing vaccines to the disease is poor understanding of the requirements for the generation of protective memory T cells (Tmem) from responding effector T cells (Teff) in chronic parasite infection. In this study, we use a transgenic mouse model with T cells specific for the merozoite surface protein (MSP)-1 of Plasmodium chabaudi to show that activated T cells generate three distinct Teff subsets with progressive activation phenotypes. The earliest observed Teff subsets (CD127(-)CD62L(hi)CD27(+)) are less divided than CD62L(lo) Teff and express memory genes. Intermediate (CD62L(lo)CD27(+)) effector subsets include the most multicytokine-producing T cells, whereas fully activated (CD62L(lo)CD27(-)) late effector cells have a terminal Teff phenotype (PD-1(+), Fas(hi), AnnexinV(+)). We show that although IL-2 promotes expansion, it actually slows terminal effector differentiation. Using adoptive transfer, we show that only early Teff survive the contraction phase and generate the terminal late Teff subsets, whereas in uninfected recipients, they become both central and effector Tmem. Furthermore, we show that progression toward full Teff activation is promoted by increased duration of infection, which in the long-term promotes Tem differentiation. Therefore, we have defined markers of progressive activation of CD4 Teff at the peak of malaria infection, including a subset that survives the contraction phase to make Tmem, and show that Ag and cytokine levels during CD4 T cell expansion influence the proportion of activated cells that can survive contraction and generate memory in malaria infection.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Memória Imunológica/imunologia , Malária/imunologia , Plasmodium chabaudi/imunologia , Subpopulações de Linfócitos T/imunologia , Transferência Adotiva , Animais , Linfócitos T CD4-Positivos/citologia , Diferenciação Celular/imunologia , Citocinas/biossíntese , Interferon gama/biossíntese , Interleucina-2/imunologia , Subunidade alfa de Receptor de Interleucina-7/metabolismo , Selectina L/metabolismo , Ativação Linfocitária/imunologia , Proteína 1 de Superfície de Merozoito/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Subpopulações de Linfócitos T/citologia , Membro 7 da Superfamília de Receptores de Fatores de Necrose Tumoral/metabolismoRESUMO
BACKGROUND: Cerebral malaria is one of the most severe complications of Plasmodium falciparum infection and occurs mostly in young African children. This syndrome results from a combination of high levels of parasitaemia and inflammation. Although parasite sequestration in the brain is a feature of the human syndrome, sequestering strains do not uniformly cause severe malaria, suggesting interplay with other factors. Host genetic factors such as mutations in the promoters of the cytokines IL-10 and TNF are also clearly linked to severe disease. Plasmodium chabaudi, a rodent malaria parasite, leads to mild illness in wildtype animals. However, IL-10(-/-) mice respond to parasite with increased levels of pro-inflammatory cytokines IFN-γ and TNF, leading to lethal disease in the absence of sequestration in the brain. These mice also exhibit cerebral symptoms including gross cerebral oedema and haemorrhage, allowing study of these critical features of disease without the influence of sequestration. METHODS: The neurological consequences of P. chabaudi infection were investigated by performing a general behavioural screen (SHIRPA). The immune cell populations found in the brain during infection were also analysed using flow cytometry and confocal microscopy. RESULTS: IL-10(-/-) mice suffer significant declines in behavioural and physical capacities during infection compared to wildtype. In addition, grip strength and pain sensitivity were affected, suggestive of neurological involvement. Several immune cell populations were identified in the perfused brain on day 7 post-infection, suggesting that they are tightly adherent to the vascular endothelium, or potentially located within the brain parenchyma. There was an increase in both inflammatory monocyte and resident macrophage (CD11b(hi), CD45(+), MHCII(+), Ly6C(+/-)) numbers in IL-10(-/-) compared to wildtype animals. In addition, the activation state of all monocytes and microglia (CD11b(int), CD45(-), MHC-II(+)) were increased. T cells making IFN-γ were also identified in the brain, but were localized within the vasculature, and not the parenchyma. CONCLUSIONS: These studies demonstrate exacerbated neuroinflammation concurrent with development of behavioural symptoms in P. chabaudi infection of IL-10(-/-) animals.
Assuntos
Comportamento Animal , Inflamação/patologia , Interleucina-10/deficiência , Malária Cerebral/complicações , Malária Cerebral/patologia , Transtornos Mentais/etiologia , Plasmodium chabaudi/crescimento & desenvolvimento , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Feminino , Citometria de Fluxo , Humanos , Leucócitos/imunologia , Malária Cerebral/parasitologia , Masculino , Camundongos Endogâmicos C57BL , Microscopia ConfocalRESUMO
Infection with the malaria parasite, Plasmodium, is characterized by excessive inflammation. The establishment of a precise balance between the pro- and anti-inflammatory responses is critical to guarantee control of the parasite and survival of the host. IL-10, a key regulatory cytokine produced by many cells of the immune system, has been shown to protect mice against pathology during acute Plasmodium0 chabaudi chabaudi AS model of malaria. However, the critical cellular source of IL-10 is still unknown. In this article, we demonstrate that T cell-derived IL-10 is necessary for the control of pathology during acute malaria, as mice bearing specific deletion of Il10 in T cells fully reproduce the phenotype observed in Il10(-)(/)(-) mice, with significant weight loss, decline in temperature, and increased mortality. Furthermore, we show that IFN-γ(+) Th1 cells are the main producers of IL-10 throughout acute infection, expressing high levels of CD44 and ICOS, and low levels of CD127. Although Foxp3(+) regulatory CD4(+) T cells produce IL-10 during infection, highly activated IFN-γ(+) Th1 cells were shown to be the essential and sufficient source of IL-10 to guarantee protection against severe immune-mediated pathology. Finally, in this model of malaria, we demonstrate that the generation of protective IL10(+)IFN-γ(+) Th1 cells is dependent on IL-27 signaling and independent of IL-21.
Assuntos
Interleucina-10/biossíntese , Interleucinas/fisiologia , Malária/imunologia , Células Th1/metabolismo , Animais , Inflamação , Interferon gama , Ativação Linfocitária/imunologia , Malária/patologia , Camundongos , Células Th1/imunologiaRESUMO
SARS-CoV-2 is a highly transmissible virus that causes COVID-19 disease. Mechanisms of viral pathogenesis include excessive inflammation and viral-induced cell death, resulting in tissue damage. We identified the host E3-ubiquitin ligase TRIM7 as an inhibitor of apoptosis and SARS-CoV-2 replication via ubiquitination of the viral membrane (M) protein. Trim7 -/- mice exhibited increased pathology and virus titers associated with epithelial apoptosis and dysregulated immune responses. Mechanistically, TRIM7 ubiquitinates M on K14, which protects cells from cell death. Longitudinal SARS-CoV-2 sequence analysis from infected patients revealed that mutations on M-K14 appeared in circulating variants during the pandemic. The relevance of these mutations was tested in a mouse model. A recombinant M-K14/K15R virus showed reduced viral replication, consistent with the role of K15 in virus assembly, and increased levels of apoptosis associated with the loss of ubiquitination on K14. TRIM7 antiviral activity requires caspase-6 inhibition, linking apoptosis with viral replication and pathology.
RESUMO
Vaccines to persistent parasite infections have been challenging, and current iterations lack long-term protection. Cytomegalovirus (CMV) chronic vaccine vectors drive protection against SIV, tuberculosis and liver-stage malaria correlated with antigen-specific CD8 T cells with a Tem phenotype. This phenotype is likely driven by a combination of antigen-specific and innate adjuvanting effects of the vector, though these mechanisms are less well understood. Sterilizing immunity from live Plasmodium chabaudi vaccination lasts less than 200 days. While P. chabaudi-specific antibody levels remain stable after vaccination, the decay of parasite-specific T cells correlates with loss of challenge protection. Therefore, we enlisted murine CMV as a booster strategy to prolong T cell responses against malaria. To study induced T cell responses, we included P. chabaudi MSP-1 epitope B5 (MCMV-B5). We found that MCMV vector alone significantly protected against a challenge P. chabaudi infection 40-60 days later, and that MCMV-B5 was able to make B5-specific Teff, in addition to previously-reported Tem, that survive to the challenge timepoint. Used as a booster, MCMV-B5 prolonged protection from heterologous infection beyond day 200, and increased B5 TCR Tg T cell numbers, including both a highly-differentiated Tem phenotype and Teff, both previously reported to protect. B5 epitope expression was responsible for maintenance of Th1 and Tfh B5 T cells. In addition, the MCMV vector had adjuvant properties, contributing non-specifically through prolonged stimulation of IFN-γ. In vivo neutralization of IFN-γ, but not IL-12 and IL-18, late in the course of MCMV, led to loss of the adjuvant effect. Mechanistically, sustained IFN-γ from MCMV increased CD8α+ dendritic cell numbers, and led to increased IL-12 production upon Plasmodium challenge. In addition, neutralization of IFN-γ before challenge reduced the polyclonal Teff response to challenge. Our findings suggest that, as protective epitopes are defined, an MCMV vectored booster can prolong protection through the innate effects of IFN-γ.
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Vascular congestion and coagulopathy have been shown to play a role in human and experimental cerebral malaria (eCM), but little is known about the role of microglia, or microglia-vascular interactions and hypercoagulation during disease progression in this fatal infection. Recent studies show microglia bind to fibrinogen, a glycoprotein involved in thrombosis. An eCM model of Plasmodium chabaudi infection in mice deficient in the regulatory cytokine IL-10 manifests neuropathology, including hypercoagulation with extensive fibrin(ogen) deposition and neuroinflammation. Intravital microscopy and immunofluorescence are applied to elucidate the role of microglia in eCM. Results show microgliosis and coagulopathy occur early in disease at 3 dpi (day post-infection), and both are exacerbated as disease progresses to 7dpi. Vessel associated microglia increase significantly at 7 dpi, and the expression of the microglial chemoattractant CCL5 (RANTES) is increased versus uninfected and localized with fibrin(ogen) in vessels. PLX3397 microglia depletion resulted in rapid behavioral decline, severe hypothermia, and greater increase in vascular coagulopathy. This study suggests that microglia play a prominent role in controlling infection-initiated coagulopathy and supports a model in which microglia play a protective role in cerebral malaria by migrating to and patrolling the cerebral vasculature, potentially regulating degree of coagulation during systemic inflammation.
Assuntos
Malária Cerebral , Camundongos , Humanos , Animais , Malária Cerebral/patologia , Microglia/metabolismo , Inflamação/patologia , Citocinas/metabolismo , Fibrina/metabolismo , Modelos Animais de Doenças , Camundongos Endogâmicos C57BLRESUMO
Protection against malaria often decays in the absence of infection, suggesting that protective immunological memory depends on stimulation. Here we have used CD4(+) T cells from a transgenic mouse carrying a T cell receptor specific for a malaria protein, Merozoite Surface Protein-1, to investigate memory in a Plasmodium chabaudi infection. CD4(+) memory T cells (CD44(hi)IL-7Rα(+)) developed during the chronic infection, and were readily distinguishable from effector (CD62L(lo)IL-7Rα(-)) cells in acute infection. On the basis of cell surface phenotype, we classified memory CD4(+) T cells into three subsets: central memory, and early and late effector memory cells, and found that early effector memory cells (CD62L(lo)CD27(+)) dominated the chronic infection. We demonstrate a linear pathway of differentiation from central memory to early and then late effector memory cells. In adoptive transfer, CD44(hi) memory cells from chronically infected mice were more effective at delaying and reducing parasitemia and pathology than memory cells from drug-treated mice without chronic infection, and contained a greater proportion of effector cells producing IFN-γ and TNFα, which may have contributed to the enhanced protection. These findings may explain the observation that in humans with chronic malaria, activated effector memory cells are best maintained in conditions of repeated exposure.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Modelos Animais de Doenças , Memória Imunológica/imunologia , Plasmodium chabaudi/imunologia , Células Th1/imunologia , Transferência Adotiva , Animais , Western Blotting , Linfócitos T CD4-Positivos/parasitologia , Linfócitos T CD4-Positivos/transplante , Proteínas de Ligação a DNA/fisiologia , Ensaio de Imunoadsorção Enzimática , Feminino , Citometria de Fluxo , Interferon gama/metabolismo , Interleucina-10/metabolismo , Malária/imunologia , Malária/patologia , Proteína 1 de Superfície de Merozoito/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Plasmodium chabaudi/crescimento & desenvolvimento , Receptores de Antígenos de Linfócitos T/fisiologia , Receptores de Interleucina-7/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
SUMMARY STATEMENT: Diabetic human and murine retinas revealed pronounced microglial morphological activation and vascular abnormalities associated with inflammation. Pharmacological fibrinogen depletion using ancrod dampened microglial morphology alterations, resolved fibrinogen accumulation, rescued axonal integrity, and reduced inflammation in the diabetic murine retina.
Assuntos
Ancrod , Retina , Animais , Receptor 1 de Quimiocina CX3C/genética , Fibrinogênio , Humanos , Inflamação/tratamento farmacológico , Camundongos , Microglia , Retina/fisiologiaRESUMO
Hybrid Th1/Tfh cells (IFN-γ+IL-21+CXCR5+) predominate in response to several persistent infections. In Plasmodium chabaudi infection, IFN-γ+ T cells control parasitemia, whereas antibody and IL-21+Bcl6+ T cells effect final clearance, suggesting an evolutionary driver for the hybrid population. We found that CD4-intrinsic Bcl6, Blimp-1, and STAT3 coordinately regulate expression of the Th1 master regulator T-bet, supporting plasticity of CD4 T cells. Bcl6 and Blimp-1 regulate CXCR5 levels, and T-bet, IL-27Rα, and STAT3 modulate cytokines in hybrid Th1/Tfh cells. Infected mice with STAT3 knockout (KO) T cells produced less antibody and more Th1-like IFN-γ+IL-21-CXCR5lo effector and memory cells and were protected from re-infection. Conversely, T-bet KO mice had reduced Th1-bias upon re-infection and prolonged secondary parasitemia. Therefore, each feature of the CD4 T cell population phenotype is uniquely regulated in this persistent infection, and the cytokine profile of memory T cells can be modified to enhance the effectiveness of the secondary response.
RESUMO
Kurup et al. (Cell Host Microbe 2019;25:565-577.e6) define the liver-based antigen-presenting cell driving CD8 T cell responses to mosquito transmission of Plasmodium spp., and show direct interaction of CD11c+ cells with infected hepatocytes. We discuss this work in context, highlighting gaps and new approaches suggested by the work to target liver-stage vaccine antigens.
Assuntos
Malária , Plasmodium , Animais , Linfócitos T CD8-Positivos , Hepatócitos , Fígado , MonócitosRESUMO
[This corrects the article DOI: 10.1371/journal.pone.0144654.].